Cash Isa to Shares ISA - would like to shelter existing non isa shareholdings

If I convert a Cash ISa to Shares ISA - what are the rules for sheltering existing shareholdings in this ISA. Obiously I declare shares I sell for capital gains -but are there any rules as to when share should be sold and bought. Can I buy shares for ISA and then sell at different dates afterwards. Or do I have to buy then sell within certain time limits. Thank you.

Hi Tessa,
You can move the contents of a cash ISA into a stocks and shares ISA without losing any of your £20000 allowance.
Have a look at the guidance here:
Individual Savings Accounts (ISAs)
Thank you.